As disclosed in Patent Document 1, for example, some conventional container refrigerators may adopt a technique for performing a variable control on their refrigeration capacity by controlling the number of rotations of a compressor motor using a power converter such as an inverter device.
Not a few of such container refrigerators operate with a generator connected thereto as their power supply. In that case, if, while the container refrigerator is operating, an inverter device is activated to control the number of rotations of its built-in compressor, then some harmonic current would be generated, since the power supplied to the built-in compressor needs to be converted through a frequency control such as a PWM control. In that case, the harmonic current could be induced in the field winding of the generator connected, for example, thus heating the rotor and other parts to raise the temperature of the generator so much as to result in a burnout.
Thus, to overcome such a problem, in compliance with the regulation established by the Japan Electrical Manufacturers' Association (JEMA) standard JEMA-1354, the harmonic current involved with the operation of the inverter device, for example, is replaced with equivalent negative-phase-sequence current such that the permissible equivalent negative-phase-sequence current flowing through the generator becomes 15% or less of the rated current of a three-phase AC generator generally used. For that reason, as the generator to be connected to the container refrigerator, a generator, of which the capacitance meets such regulation, needs to be selected.